1. Field of the Invention
The present invention relates to surge protection, and more particularly to a surge protector that utilizes a non-linear surge suppression circuit with a series connected transformer. This surge protector is useful for single phase service, and is useful in three phase service applications wherein three transformers (one for each hot line) are used. In the three phase service surge protector of the present invention canceling signals are added by each transformer output.
2. Information Disclosure Statement
The following prior art is representative of the state of the art in the field of surge protection:
U.S. Pat. No. 4,870,528 discloses a surge suppressor comprises a first series circuit having a first inductance and a first alternating voltage limiter, including at least a first capacitance and a bidi-rectionally conductive rectifying circuit for charging the first capacitance, coupled between first and second input terminals for limiting surge currents and voltage excursions coupled to first and second load output terminals. The first alternating voltage limiter further comprises a sensing circuit for sensing at least one of the charging current supplied to and the voltage developed across the first capacitance. An auxiliary energy storage circuit and a normally open switching device responsive to the sensing circuit are provided for coupling the auxiliary energy storage circuit across the first capacitance during high energy surge conditions.
U.S. Pat. No. 4,870,534 discloses a surge suppressor for repeatedly protecting a load against surges occurring on A-C power mains from lightning surges. It includes a first series circuit having a first inductance and a first alternating voltage limiter, including at least a first capacitance and a bidirectionally conductive rectifier circuit, coupled between first and second input terminals. The first inductance conducts substantially all of the current supplied from the A-C power mains. A second series circuit comprising a second inductance and second alternating voltage limiter, including at lest a second capacitance and a second bidirectionally conductive rectifier circuit, is coupled across the first alternating voltage limiter and is coupled to first and second output terminals. The first voltage excursions passed to the second series circuit to first levels while the second series circuit is arranged for further limiting surge currents and voltage excursions passed to the output terminals to second levels less than first levels.
U.S. Pat. No. 5,617,284 discloses a power surge protection apparatus that protects circuitry from electrical surges induced in an alternating current power connection to the circuity. The apparatus includes first, second, and third stages, which serve to clamp and dissipate superfluous energy, such as that from a power surge, on the power connection. The first stage comprises a metal oxide varistor MOV 1 and a capacitor for helping to clamp and dissipate large-duration continuous surges on the power connection. The second stage comprises an RC-LC filter with resistor R1, capacitor C2, inductor L1, and capacitor C3. Moreover, the second stage has a metal oxide varistor MOV 2. The second stage further comprises a bifilar transformer T1 situated between the connections. Specifically, the inductors of the bifilar transformer T1 are disposed in series with the connections of the power connection, and the connections are twisted about each other and wrapped in a bifilar winding configuration about a common core.
U.S. Pat. No. 5,621,625 discloses a surge protection circuit for switching mode power supply utilizing the switching phase difference of substantially 180 degree between primary and secondary coils of a switching power supply transformer that snubs transformer by attenuating the surges induced during ON/OFF operations of a switching transistor which controls the power supply transformer. Accordingly, heat caused during the ON/OFF operation of the switching transistor is reduced and secondary rectifier diodes connected to the secondary winding of the power transformer are protected from damages. The surge protection circuit uses a pair of capacitors connected in series between a control terminal of the primary coil and an output terminal of the secondary coil of the switching power supply transformer for snubbing bi-directional surges induced by the ON/OFF operation of the switching transistor.
U.S. patent application Disclosure No. 2003/0165035 A1 describes a system and method for conditioning a power transmission, thereby eliminating adverse characteristics from the power transmission. The system selectively includes a voltage surge protector, and EMI/RFI filter and at lest one inrush current suppressor integrally formed into a single system. To condition an incoming power transmission, the power transmission is passed through the voltage surge protector to eliminate any abnormal voltage spikes. The power transmission is then passed through an improved EMI/RFI filter having a dual output. The outputs of the EMI/RFI filter lead into a first inrush current suppressor. The inrush current suppressor limits the amperage of the power transmission for a predetermined period of time and then permits unrestricted current flow.
U.S. patent application Disclosure No. 2004/0004799 A1 describes a surge suppression device includes a first and second coil positioned in close proximity to one another such that the windings of each coil are disposed at an angle thereto. In a preferred embodiment, the coils are disposed such that the windings of each coil are placed at a right angle (90 degrees) to one another. However, angles of varying degree can be employed. Varying configurations of the coil winding placement include a “sandwiched” type configuration, a “one on the top of the other” configuration as well as an intertwined configuration. Each embodiment employs additional surge elements such as metal oxide varistors (MOVs). It is unnecessary to employ any ferrous material core for any of the coils used in the novel device of the present invention.
Notwithstanding the prior art, the present invention is neither taught nor rendered obvious thereby.